At present, a reinforcing member for a carcass constituting a skeleton of a radial tire for passenger vehicle, in particular, a belt which is generally used as a reinforcing member for a crown portion of a carcass is mainly constituted such that two or more steel belt layers composed of layers in which rubberized steel cord obliquely arranged with respect to the tire equatorial plane are used, and that the steel cords in the belt layers are crossed each other.
Conventionally, for the improvement of a belt layer, a variety of studies have been conducted. For example, Patent Document 1 discloses a technique in which several reinforcing elements are used to form a bundle and the bundles are embedded in a belt at a constant interval to improve the durability of the belt. Patent Document 2 discloses that, by using as a belt reinforcing material a steel cord having (1×2) structure, separation which occurs at the belt edge can be inhibited and the weight of a tire is reduced.